The present invention is directed to a deflectable catheter with a tip section having varying degrees of stiffness.
Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, an electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart which is of concern. The catheter should preferably be deflectable to permit proper positioning of the electrodes on its distal end within the heart.
Deflectable tip electrode catheters are well known. Such a catheter generally has a control handle at its proximal end for controlling deflection of the tip in one or more directions. For example, a particularly useful deflectable tip catheter is disclosed in U.S. Pat. No. Re. 34,502 to Webster, the disclosure of which is hereby incorporated by reference. This catheter comprises a puller wire that extends on-axis through an elongated reinforced catheter body and then off-axis in a deflectable tip portion. In this arrangement, longitudinal movement of the puller wire relative to the catheter body results in deflection of the catheter tip portion. Other examples of steerable catheters can be found in U.S. Pat. No. 5,431,168 to Webster entitled xe2x80x9cSteerable Open-Lumen Catheterxe2x80x9d and U.S. patent application Ser. No. 08/924,611 to Webster entitled xe2x80x9cOmni-Directional Steerable Catheter,xe2x80x9d the disclosures of which are hereby incorporated by reference.
One drawback to deflectable catheters is the kinking effect that can result when the distal end or tip section of the catheter is deflected. Frequently, the tip section of the catheter is made of a material considerably more flexible than the catheter body. As a result, the junction between the catheter body and the tip section tends to kink or bend when the tip section is deflected.
The present invention provides a deflectable tip catheter having a comfortable, ergonomic handle. In one embodiment, the deflectable tip catheter comprises a catheter body, a tip section, and an ergonomic control handle. The catheter body has proximal and distal ends and at least one lumen extending therethrough. The tip section similarly comprises proximal and distal ends and at least one lumen extending therethrough. The proximal end of the tip section is fixedly attached to the distal end of the catheter body.
The control handle comprises a housing having a generally hollow interior, a piston receiving assembly at least partially within the interior of the housing, and a piston. The piston receiving assembly is afforded rotational movement relative to the housing. The piston receiving assembly comprises a generally tubular member defining a piston chamber. The piston is fixedly attached to the proximal end of the catheter body and extends into the piston chamber of the piston receiving assembly. The piston is afforded longitudinal movement relative to the piston receiving assembly but is not afforded rotational movement relative to the piston receiving assembly. Accordingly, rotation of the piston relative to the housing correspondingly rotates the piston receiving assembly, catheter body and tip section. By this design, the user can hold the handle in a stationary position and rotate the catheter body and tip section by merely rotating the piston. Previous designs, e.g., as discussed in U.S. Pat. No. Re 34,502, required that the user rotate the entire handle, include the housing, to rotate the catheter body and tip section.
To deflect the tip section, a puller wire having proximal and distal ends extends from the control handle, through a lumen in the catheter body and into a lumen in the tip section. The proximal end of the puller wire is anchored in the control handle, preferably in the piston receiving assembly, so that distal movement of the piston relative to the piston receiving assembly results in distal movement of the catheter body relative to the puller wire. Means are provided for deflecting the tip section in response to distal movement of the catheter body relative to the puller wire. A preferred deflecting means comprises an off-axis lumen in the tip section into which the puller wire extends and an anchor that anchors the puller wire to the tip section. Another deflecting means is described in U.S. Pat. Nos. 5,336,182 and 5,364,351, the disclosures of which are incorporated herein by reference.
In a particularly preferred embodiment, the handle housing comprises a generally cylindrical distal portion and a curved proximal portion for gripping. To permit the user to hold the handle in a stationary position while rotating the catheter body and tip section, a novel piston receiving assembly is provided. The piston receiving assembly comprises a rigid tubular distal barrel and means for carrying electrode lead wires, a sensor cable and thermocouple wires from the distal barrel to a connecter at the proximal end of the handle. The distal barrel, which lies within the handle housing, is generally tubular at its distal end, forming a piston chamber therein. A preferred carrying means comprises a rigid proximal barrel connected to the distal barrel, preferably by a universal coupling. The proximal barrel, which is contained at least in part within the handle housing, is generally tubular. By means of the universal coupling, rotation of the distal barrel results in corresponding rotation of the proximal barrel.
A particularly preferred deflectable catheter comprises a tip section having varying stiffness. The tip section comprises a flexible tubing having proximal and distal ends and at least two lumens extending therethrough. The flexible tubing has at least two different stiffnesses, and preferably three to five different stiffnesses, along its length. In a particularly preferred embodiment, the flexible tubing comprises a plastic core, a metal braid over the core, a plastic skin over the braid, and at least two, and preferably three to five, pieces of plastic tubing in longitudinal arrangement extruded over the plastic skin. The pieces of plastic tubing have different stiffnesses and are arranged with the stiffer tubing being proximal the less stiff tubing.
A preferred method for making a catheter tip section of varying stiffness comprises extruding a plastic core over at least two, and preferably three, mandrels, thereby forming lumens. Preferably metal is braided over the plastic core. Thereafter, at least two, and preferably three to five, pieces of plastic tubing having different degrees of stiffness are assembled along the length of the plastic core so that the piece of plastic tubing having the greatest stiffness is at the proximal end of the tip section and the piece of plastic having the lowest stiffness is near the distal end of the tip section. The pieces of plastic tubing are then melted to bond with the plastic core.
A particularly preferred method comprises first extruding a plastic core over at least two mandrels. Metal is braided over the plastic core. Thereafter, a thin skin of plastic is extruded over the metal braid to form an inner core. At least two, and preferably three to five, pieces of plastic tubing having different degrees of stiffness are assembled in surrounding relation to the inner core to form an assembly where the piece of plastic tubing having the greatest stiffness is at the proximal end of the assembly and the piece of plastic having the lowest stiffness is near the distal end of the assembly. A shrink sleeve is placed over the entire assembly. The pieces of plastic tubing are then heated sufficiently to bond them to the inner core, and the shrink sleeve is then removed.